Young Socceroos goalkeeper Mat Ryan admits the World Cup has been an eye-opener to what it takes to compete with the international elite.

After having nine goals put past him in Australia's three defeats, including the 3-0 loss to Spain on Tuesday (AEST), the 22-year-old gloveman has vowed to learn from the harsh lessons in Brazil.

"It's been a massive eye-opener for me, coming to this top level and seeing the individuals we're up against," said Ryan.

"They're unbelievably talented, and it's a massive learning experience to see the skills they possess and the speed they have.

"Conceding three goals in every game just isn't good enough. It's a real eye-opener and I have to work really hard on my game to improve."

Ryan arrived in Brazil as Ange Postecoglou's clear choice to fill Mark Schwarzer's shoes, coming off a standout maiden campaign in the Belgium top flight where he was named goalkeeper of the year for his work at Club Brugge.

But coming up against some of the world's best attackers in Chile's Barcelona star Alexis Sanchez, Dutch duo Robin van Persie and Arjen Robben and Spain's endless list of superstars including David Villa, Fernando Torres and Juan Mata was another huge step up.

Ryan was certainly not to blame for all nine goals Australia conceded, though he admits his blunder that gifted Holland the winner in Australia's heartbreaking 3-2 loss fuelled him to do better against Spain.

Despite a better showing, Ryan could do little to stop the fierce attacking firepower of the chastened world No 1 side.

"After what happened with the third goal against Holland, I had to come out today with a bit of a reaction," he said.

"The first 45 minutes was probably the most comfortable for me in the whole tournament, it felt like my best."

The former Central Coast Mariners goalkeeper said his experience in Brazil showed him how far he still has to go to match it with the best.

"Now I have to go and assess my performance, look at what I can do better to improve, and ultimately do better against these world class players in such situations.

"I know I have to improve my shot-stopping, improve every aspect if I want to match these guys."

Australian coach Ange Postecoglou says his players were spent. He blames fatigue for basic blunders in a 3-0 loss to Spain in the last match of their World Cup campaign.

"These guys, this has been a massive effort both physically, mentally, emotionally - three massive games," Postecoglou told reporters.

"But that is the level that we have to perform at, there's no hiding from it, that is the level we have got to reach.

"They really struggled, particularly after the first 10, 15 minutes, to have the effort that was required.

"And we lost our discipline, our decision-making wasn't great, we gave the ball away far too cheaply, which we haven't been doing in this tournament."

Postecoglou said his Socceroos were dominated by Spain after a bright opening - and the statistics from the encounter at Curitiba's Arena da Baixada support his summation.

The Socceroos couldn't muster a shot on target, while Spain recorded 11 - three of which hit the net.

All of Spain's goals slipped through a leaky Australian defence; the Socceroos' midfield was overwhelmed; and without suspended striker Tim Cahill there was no real threat in attack. - AAP